334 THE SUPPOSED PERMANENCE [CHAP. XV. 



Europe, Asia, and Africa, or bear any other definite rela- 

 tion to these continents. 



If these inferences are correct, may we not deduce the 

 still more comprehensive conclusion, that the deep ocean- 

 basins and lofty mountain ranges of the modern world 

 have been formed by a long process of geographical evolu- 

 tion, which has proceeded pari passu with the development 

 and differentiation of the animals and plants which in- 

 habit them, the tendency of all recent geographical 

 changes having been to deepen the ocean-basins and to 

 raise the mountain-peaks to higher and higher elevations. 



This theory has at any rate the advantage of being 

 based on definite facts, of reconciling many points of 

 difficulty, of avoiding extremes, and of being in accordance 

 with the general principle of Evolution. I state it in order 

 that it may receive consideration from capable critics, and 

 time will prove whether or not it is a tenable view. That 

 it avoids the two extremes of complete permanence and 

 frequent interchange is by no means its least recom- 

 mendation, for the history of scientific controversies shows 

 that antagonistic views have often been reconciled by an 

 hypothesis which concedes something to both sides, for 

 scientific men are not exempt from the common failing of 

 veering too rapidly from one extreme to another, when in 

 so many cases the truth lies midway between the extreme 

 views. The advice which Horace gave to his friend Licinius, 

 and which Ovid so tersely expresses by the words, 



" medio tutissimus ibis," 



is equally applicable to the ways of science and philosophy. 

 Thus I feel convinced that the truth is neither with those 

 who assert the complete permanence of oceans and conti- 

 nents, nor with those who teach the frequent conversion of 

 one into the other. Similarly, that the existence of the 

 calcareous ooze in modern oceans should be regarded as 



